Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Derivative Asset, Current	$ 33	$ 0
Derivative Asset, Noncurrent	54	0
Liabilities:
Commodity derivative liabilities – current	63,257	27,777
Derivative Liability, Noncurrent	29,566	13,900
Fair Value, Measurements, Recurring \| Commodity contracts
Assets:
Derivative Asset, Current	33
Derivative Asset, Noncurrent	54
Liabilities:
Commodity derivative liabilities – current	63,257	27,777
Derivative Liability, Noncurrent	29,566	13,900
Fair Value, Measurements, Recurring \| Commodity contracts \| Level 1
Assets:
Derivative Asset, Current	0
Derivative Asset, Noncurrent	0
Liabilities:
Commodity derivative liabilities – current	0	0
Derivative Liability, Noncurrent	0	0
Fair Value, Measurements, Recurring \| Commodity contracts \| Level 2
Assets:
Derivative Asset, Current	33
Derivative Asset, Noncurrent	54
Liabilities:
Commodity derivative liabilities – current	63,257	27,777
Derivative Liability, Noncurrent	29,566	13,900
Fair Value, Measurements, Recurring \| Commodity contracts \| Level 3
Assets:
Derivative Asset, Current	0
Derivative Asset, Noncurrent	0
Liabilities:
Commodity derivative liabilities – current	0	0
Derivative Liability, Noncurrent	$ 0	$ 0

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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